20 found
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  1. Almost Everywhere Equivalence of Logics in Finite Model Theory.Lauri Hella, Phokion G. Kolaitis & Kerkko Luosto - 1996 - Bulletin of Symbolic Logic 2 (4):422-443.
    We introduce a new framework for classifying logics on finite structures and studying their expressive power. This framework is based on the concept of almost everywhere equivalence of logics, that is to say, two logics having the same expressive power on a class of asymptotic measure 1. More precisely, if L, L ′ are two logics and μ is an asymptotic measure on finite structures, then $\scr{L}\equiv _{\text{a.e.}}\scr{L}^{\prime}(\mu)$ means that there is a class C of finite structures with μ (C)=1 (...)
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  2. The Hierarchy Theorem for Generalized Quantifiers.Lauri Hella, Kerkko Luosto & Jouko Väänänen - 1996 - Journal of Symbolic Logic 61 (3):802-817.
    The concept of a generalized quantifier of a given similarity type was defined in [12]. Our main result says that on finite structures different similarity types give rise to different classes of generalized quantifiers. More exactly, for every similarity type t there is a generalized quantifier of type t which is not definable in the extension of first order logic by all generalized quantifiers of type smaller than t. This was proved for unary similarity types by Per Lindström [17] with (...)
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  3.  5
    Definability Hierarchies of Generalized Quantifiers.Lauri Hella - 1989 - Annals of Pure and Applied Logic 43 (3):235-271.
  4. Notions of Locality and Their Logical Characterizations Over Finite Models.Lauri Hella, Leonid Libkin & Juha Nurmonen - 1999 - Journal of Symbolic Logic 64 (4):1751-1773.
    Many known tools for proving expressibility bounds for first-order logic are based on one of several locality properties. In this paper we characterize the relationship between those notions of locality. We note that Gaifman's locality theorem gives rise to two notions: one deals with sentences and one with open formulae. We prove that the former implies Hanf's notion of locality, which in turn implies Gaifman's locality for open formulae. Each of these implies the bounded degree property, which is one of (...)
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  5.  52
    Definability of Polyadic Lifts of Generalized Quantifiers.Lauri Hella, Jouko Väänänen & Dag Westerståhl - 1997 - Journal of Logic, Language and Information 6 (3):305-335.
    We study generalized quantifiers on finite structures.With every function : we associate a quantifier Q by letting Q x say there are at least (n) elementsx satisfying , where n is the sizeof the universe. This is the general form ofwhat is known as a monotone quantifier of type .We study so called polyadic liftsof such quantifiers. The particular lifts we considerare Ramseyfication, branching and resumption.In each case we get exact criteria fordefinability of the lift in terms of simpler quantifiers.
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  6.  3
    The Expressive Power of Modal Dependence Logic.Lauri Hella, Kerkko Luosto, Katsuhiko Sano & Jonni Virtema - 2014 - In Rajeev Goré, Barteld Kooi & Agi Kurucz (eds.), Advances in Modal Logic, Volume 10. CSLI Publications. pp. 294-312.
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  7.  7
    How to Define a Linear Order on Finite Models.Lauri Hella, Phokion G. Kolaitis & Kerkko Luosto - 1997 - Annals of Pure and Applied Logic 87 (3):241-267.
    We carry out a systematic investigation of the definability of linear order on classes of finite rigid structures. We obtain upper and lower bounds for the expressibility of linear order in various logics that have been studied extensively in finite model theory, such as least fixpoint logic LFP, partial fixpoint logic PFP, infinitary logic Lω∞ω with a finite number of variables, as well as the closures of these logics under implicit definitions. Moreover, we show that the upper and lower bounds (...)
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  8.  32
    Capturing Relativized Complexity Classes Without Order.Anuj Dawar, Georg Gottlob & Lauri Hella - 1998 - Mathematical Logic Quarterly 44 (1):109-122.
    We consider the problem of obtaining logical characterisations of oracle complexity classes. In particular, we consider the complexity classes LOGSPACENP and PTIMENP. For these classes, characterisations are known in terms of NP computable Lindström quantifiers which hold on ordered structures. We show that these characterisations are unlikely to extend to arbitrary structures, since this would imply the collapse of certain exponential complexity hierarchies. We also observe, however, that PTIMENP can be characterised in terms of Lindström quantifers , though it remains (...)
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  9.  5
    The Hierarchy Theorem for Generalized Quantifiers.Lauri Hella, Kerkko Luosto & Jouko Vaananen - 1996 - Journal of Symbolic Logic 61 (2):802-817.
    The concept of a generalized quantifier of a given similarity type was defined in [12]. Our main result says that on finite structures different similarity types give rise to different classes of generalized quantifiers. More exactly, for every similarity type $t$ there is a generalized quantifier of type $t$ which is not definable in the extension of first order logic by all generalized quantifiers of type smaller than $t$. This was proved for unary similarity types by Per Lindstrom [17] with (...)
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  10.  20
    Remarks on The Cartesian Closure.Lauri Hella & Michal Krynicki - 1991 - Zeitschrift fur mathematische Logik und Grundlagen der Mathematik 37 (33-35):539-545.
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  11.  6
    Partially Ordered Connectives and Finite Graphs.Lauri Hella & Gabriel Sandu - 1995 - In M. Krynicki, M. Mostowski & L. Szczerba (eds.), Quantifiers: Logics, Models and Computation. Kluwer Academic Publishers. pp. 79--88.
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  12.  16
    Vectorization Hierarchies of Some Graph Quantifiers.Lauri Hella & Juha Nurmonen - 2000 - Archive for Mathematical Logic 39 (3):183-207.
    We give a sufficient condition for the inexpressibility of the k-th extended vectorization of a generalized quantifier $\sf Q$ in ${\rm FO}({\vec Q}_k)$ , the extension of first-order logic by all k-ary quantifiers. The condition is based on a model construction which, given two ${\rm FO}({\vec Q}_1)$ -equivalent models with certain additional structure, yields a pair of ${\rm FO}({\vec Q}_k)$ -equivalent models. We also consider some applications of this condition to quantifiers that correspond to graph properties, such as connectivity and (...)
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  13.  14
    The Beth-Closure of $Mathscr{L}(Q_alpha)$ is Not Finitely Generated.Lauri Hella & Kerkko Luosto - 1992 - Journal of Symbolic Logic 57 (2):442-448.
    We prove that if $\aleph_\alpha$ is uncountable and regular, then the Beth-closure of $\mathscr{L}_{\omega\omega}(Q_\alpha)$ is not a sublogic of $\mathscr{L}_{\infty\omega}(\mathbf{Q}_n)$, where $\mathbf{Q}_n$ is the class of all $n$-ary generalized quantifiers. In particular, $B(\mathscr{L}_{\omega\omega}(Q_\alpha))$ is not a sublogic of any finitely generated logic; i.e., there does not exist a finite set $\mathbf{Q}$ of Lindstrom quantifiers such that $B(\mathscr{L}_{\omega\omega}(Q_\alpha)) \leq \mathscr{L}_{\omega\omega}(\mathbf{Q})$.
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  14.  16
    Remarks on The Cartesian Closure.Lauri Hella & Michal Krynicki - 1991 - Mathematical Logic Quarterly 37 (33‐35):539-545.
  15.  32
    Partially Ordered Connectives and Monadic Monotone Strict Np.Lauri Hella, Merlijn Sevenster & Tero Tulenheimo - 2008 - Journal of Logic, Language and Information 17 (3):323-344.
    Motivated by constraint satisfaction problems, Feder and Vardi (SIAM Journal of Computing, 28, 57–104, 1998) set out to search for fragments of satisfying the dichotomy property: every problem definable in is either in P or else NP-complete. Feder and Vardi considered in this connection two logics, strict NP (or SNP) and monadic, monotone, strict NP without inequalities (or MMSNP). The former consists of formulas of the form , where is a quantifier-free formula in a relational vocabulary; and the latter is (...)
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  16.  18
    The Beth-Closure of L(Qα) is Not Finitely Generated.Lauri Hella & Kerkko Luosto - 1992 - Journal of Symbolic Logic 57 (2):442 - 448.
    We prove that if ℵα is uncountable and regular, then the Beth-closure of Lωω(Qα) is not a sublogic of L∞ω(Qn), where Qn is the class of all n-ary generalized quantifiers. In particular, B(Lωω(Qα)) is not a sublogic of any finitely generated logic; i.e., there does not exist a finite set Q of Lindstrom quantifiers such that B(Lωω(Qα)) ≤ Lωω(Q).
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  17.  11
    A Double Arity Hierarchy Theorem for Transitive Closure Logic.Martin Grohe & Lauri Hella - 1996 - Archive for Mathematical Logic 35 (3):157-171.
    In this paper we prove that thek-ary fragment of transitive closure logic is not contained in the extension of the (k−1)-ary fragment of partial fixed point logic by all (2k−1)-ary generalized quantifiers. As a consequence, the arity hierarchies of all the familiar forms of fixed point logic are strict simultaneously with respect to the arity of the induction predicates and the arity of generalized quantifiers.Although it is known that our theorem cannot be extended to the sublogic deterministic transitive closure logic, (...)
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  18.  7
    Stål Anderaa (Oslo), A Traktenbrot Inseparability Theorem for Groups. Peter Dybjer (G Öteborg), Normalization by Yoneda Embedding (Joint Work with D. Cubric and PJ Scott). Abbas Edalat (Imperial College), Dynamical Systems, Measures, Fractals, and Exact Real Number Arithmetic Via Domain Theory. [REVIEW]Anita Feferman, Solomon Feferman, Robert Goldblatt, Yuri Gurevich, Klaus Grue, Sven Ove Hansson, Lauri Hella, Robert K. Meyer & Petri Mäenpää - 1997 - Bulletin of Symbolic Logic 3 (4).
  19.  4
    The Size of a Formula as a Measure of Complexity.Jouko Väänänen & Lauri Hella - 2015 - In Andrés Villaveces, Roman Kossak, Juha Kontinen & Åsa Hirvonen (eds.), Logic Without Borders: Essays on Set Theory, Model Theory, Philosophical Logic and Philosophy of Mathematics. De Gruyter. pp. 193-214.
  20.  3
    Finite Generation Problem and N-Ary Quantifiers.Lauri Hella & Kerkko Luosto - 1995 - In M. Krynicki, M. Mostowski & L. Szczerba (eds.), Quantifiers: Logics, Models and Computation. Kluwer Academic Publishers. pp. 63--104.
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